The present invention relates to a method for the preparation of a cycloalkyl silane compound or, more particularly, to a method for the preparation of a cycloalkyl silane compound having a saturated cyclic group, which is useful as an intermediate for the synthesis of various kinds of organopolysilanes, organopolysiloxanes and as a silylating agent having stereospecificity, by the hydrosilylation reaction between an unsaturated cyclic hydrocarbon compound such as cyclohexene and a hydrogen silane compound in the presence of a platinum catalyst.
It is well known that a cycloalkyl silane compound having a saturated cyclic hydrocarbon group, such as a cyclohexyl silane compound, can be obtained by the hydrosilylation reaction between an unsaturated cyclic hydrocarbon compound such as cyclohexene and a hydrogen silane compound such as methyl dichlorosilane in the presence of a platinum catalyst. The yield of the desired product is usually low in the above mentioned prior art method and it is generally understood that the yield can be noticeably increased only with extreme difficulties.
To describe a particular prior art method for the preparation of a cycloalkyl silane compound, it has been reported in Journal of the American Chemical Society, volume 79, page 947 (1975) that methyl cyclohexyl dichlorosilane can be obtained almost quantitatively by the reaction of cyclohexene and methyl dichlorosilane in the presence of chloroplatinic acid H.sub.2 PtCl.sub.6.6H.sub.2 O when the mixture is sealed in a glass ampule and heated in boiling water for 20 hours. This result is, however, not reproducible and the result of the subsequently repeated experiments was that the highest yield of the desired reaction product was only about 15% in the reaction mixture and the reaction could proceed no longer even by further continued heating of the mixture. It is also reported in U.S. Pat. No. 3,220,972 that the same cycloalkyl silane compound can be obtained in a yield of 50% by the hydrosilylation reaction of cyclohexene and methyl dichlorosilane in a glass ampule at 100.degree. C. for 6 hours when the reaction is carried out in the presence of an activated platinum catalyst prepared by a heat treatment of a mixture of chloroplatinic acid and n-octyl alcohol followed by removal of hydrogen chloride, water and unreated n-octyl alcohol. This method is also not quite satisfactory because a yield of larger than 50% of the desired product can hardly be obtained due to the deactivation of the platinum catalyst in the course of the reaction.
An attempt has been made and reported in Journal of Organometallic Chemistry, volume 50, page 297 (1973) to perform the above mentioned hydrosilylation reaction in the presence of a nickel complex as the catalyst. This method is industrially not practicable because by-products are necessarily produced in large amounts.
Thus, the only method for the industrial production of a cycloalkyl silane compound having a saturated cyclic hydrocarbon group is the Grignard reaction between a halogen-containing saturated hydrocarbon compound such as chlorocyclohexane and an alkyl halogenosilane such as methyl trichlorosilane. This method by the Grignard reaction is industrially not quite satisfactory in respect of the productivity because the reaction must be performed by diluting the reaction mixture with a large volume of a solvent and a magnesium salt is always produced as a by-product and precipitated in the reaction mixture so that expensive facilities must be provided for the recovery of the solvent and separation of the precipitated magnesium salt leading to an increase in the production cost of the product if not to mention the yield of the desired product which cannot be high enough inherently.